#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <utility>
#include <string>
#include <queue>
#include <stack>
#include <unordered_set>
#include <unordered_map>

using namespace std;

typedef long long int ll;
typedef pair<int, int> Pii;

const ll mod = 998244353;

ll modpow(ll a, ll b, ll m = mod) {
  ll r = 1;
  while (b > 0) {
    if (b & 1) r = (r * a) % m;
    a = (a * a) % m;
    b >>= 1;
  }
  return r;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  
  string s;
  cin >> s;

  int n = s.size();

  ll ans = 0;
  ll m_count = 0;
  for (int i = 0; i < n; i++) {
    if (s[i] == 'M') {
      m_count++;
    }
    else {
      ans = (ans + modpow(3, m_count)) % mod;
    }
  }

  cout << ans << endl;

  return 0;
}